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3.2.5 X3A SIN/COS-SSI
Encoder
The SIN/COS-SSI encoder provides two differential analog channels
for incremental position and one serial data channel with clock for
communication with the encoder. This serial data channel can provide
the drive with the absolute position of the motor.
The analog cosine and sine wave signals of tracks A and B have a
voltage of 1 Vpp with an Offset of 2.5 V. This analog voltage is measured
and a high resolution position value is determined as a result. This high
resolution position value is very important for good speed control of a
gearless motor.
Therefore it is absolutely necessary to ensure these signals are well
shielded! Noise on the analog signals resulting from breaks in the
shield or improper shield termination will result in vibration in the
motor and poor ride quality.
During start-up and then every 30 ms a request is transmitted to the
encoder and the absolute position is read out via serial communication.
This initial readout of the absolute position provides the drive with the
commutation angle for permanent magnet motors. On the very  rst
operation of a permanent magnet motor it is necessary to synchronize
the encoder position to one of the pole pairs of the motor. See parameter
LF.77 for more information and section 5.11.1.
During normal operation, the difference between the internal absolute
position of the encoder and the measured position value in the drive is
compared. If the two deviate by more than 2.8 degrees, the drive will trigger
the error, E.ENCC. Refer to parameter LF.26 for more information.
The clock signal serves as synchronisation for the serial data channel.
If there is an excess length of cable (10 feet or less), it is OK to coil it into
a loop in the controller. Maintain a minimum diameter of 1 foot and keep
the cable at least 8 inches away from all high voltage power wires.
i
Installation and Connection
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